Playfair cipher: Difference between revisions
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(→{{header|REXX}}: added a thank you in the REXX section header, added a literal to make a couple of error messages easier to peruse (in the program). -- ~~~~) |
(→{{header|REXX}}: extended the REXX pgm to allow a multi-word cipher (which necessitated changing the order of the 1st two variables). -- ~~~~) |
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<br>For ease of viewing and comparing, the output is in capitalized digraphs (which are really ''digrams'') as well as the original input(s). |
<br>For ease of viewing and comparing, the output is in capitalized digraphs (which are really ''digrams'') as well as the original input(s). |
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<br>Thanks to Walter Pachl, this program is now sensitive of using a suitable ''double character'' when '''X''' is present in the cipher key. |
<br>Thanks to Walter Pachl, this program is now sensitive of using a suitable ''double character'' when '''X''' is present in the cipher key. |
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<br>Also, more thanks are due to Walter Pachl |
<br>Also, more thanks are due to Walter Pachl for finding that the cipher key can't contain the OMIT character. |
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<br> |
<br>A fair amount of code was added to massage the decrypted encryption to remove doubled '''X'''es so as to match the original text |
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<br>(this is the ''possible text'' part of the REXX code). |
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<lang rexx>/*REXX program implements a PLAYFAIR cipher (encryption & decryption).*/ |
<lang rexx>/*REXX program implements a PLAYFAIR cipher (encryption & decryption).*/ |
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@abc='abcdefghijklmnopqrstuvwxyz'; @abcU=@abc /*lower and upper ABC's.*/ |
@abc='abcdefghijklmnopqrstuvwxyz'; @abcU=@abc /*lower and upper ABC's.*/ |
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parse arg |
parse arg omit key '(' text /*TEXT is the phrase to be used. */ ;oldK=key /*save old.*/ |
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if key =='' | key ==',' then do; key='Playfair example.'; oldK=key " ◄───using the default."; end |
if key =='' | key ==',' then do; key='Playfair example.'; oldK=key " ◄───using the default."; end |
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if omit=='' | omit==',' then omit='J' /*the "omitted" character. */ |
if omit=='' | omit==',' then omit='J' /*the "omitted" character. */ |
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newKey =scrub(key , 1) /*scrub old cipher key──► newKey */ |
newKey =scrub(key , 1) /*scrub old cipher key──► newKey */ |
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newText=scrub(text ) /* " " text ──► newText*/ |
newText=scrub(text ) /* " " text ──► newText*/ |
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if _\=='' then call err 'too many arguments specified.' |
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if newText=='' then call err 'TEXT is empty or has no letters' |
if newText=='' then call err 'TEXT is empty or has no letters' |
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if length(omit)\==1 then call err 'OMIT letter must be only one letter' |
if length(omit)\==1 then call err 'OMIT letter must be only one letter' |
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════════════════Playfair encryption──► decryption──► encryption worked. |
════════════════Playfair encryption──► decryption──► encryption worked. |
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</pre> |
</pre> |
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'''output''' when using the input of: <tt> |
'''output''' when using the input of: <tt> x stuvw (myteest </tt> |
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<pre> |
<pre> |
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old cipher key: stuvw |
old cipher key: stuvw |
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